JP2018066040A - HOT-ROLLED SHEET ANNEALING FACILITY OF Si-CONTAINING HOT-ROLLED STEEL SHEET, HOT-ROLLED SHEET ANNEALING METHOD AND DESCALING METHOD - Google Patents

HOT-ROLLED SHEET ANNEALING FACILITY OF Si-CONTAINING HOT-ROLLED STEEL SHEET, HOT-ROLLED SHEET ANNEALING METHOD AND DESCALING METHOD Download PDF

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JP2018066040A
JP2018066040A JP2016205194A JP2016205194A JP2018066040A JP 2018066040 A JP2018066040 A JP 2018066040A JP 2016205194 A JP2016205194 A JP 2016205194A JP 2016205194 A JP2016205194 A JP 2016205194A JP 2018066040 A JP2018066040 A JP 2018066040A
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hot
rolled
steel sheet
heating
descaling
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JP6748375B2 (en
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剛毅 山田
Goki YAMADA
剛毅 山田
悦充 原田
Etsumitsu Harada
悦充 原田
隆浩 高津
Takahiro Takatsu
隆浩 高津
松原　行宏
Yukihiro Matsubara
行宏 松原
雄太 田村
Yuta Tamura
雄太 田村
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JFE Steel Corp
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Priority to JP2016205194A priority Critical patent/JP6748375B2/en
Priority to KR1020197009164A priority patent/KR102292306B1/en
Priority to PCT/JP2017/036766 priority patent/WO2018074295A1/en
Priority to RU2019115127A priority patent/RU2724265C1/en
Priority to US16/343,217 priority patent/US20190249270A1/en
Priority to CN201780063342.XA priority patent/CN109844143B/en
Priority to EP17861698.3A priority patent/EP3530762B1/en
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/82—Descaling by thermal stresses
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
    • C21D8/1261—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1277—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a particular surface treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0062—Heat-treating apparatus with a cooling or quenching zone
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/60—Continuous furnaces for strip or wire with induction heating
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/62—Continuous furnaces for strip or wire with direct resistance heating
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/40—Direct resistance heating
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/42—Induction heating
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Abstract

PROBLEM TO BE SOLVED: To provide a hot-rolled sheet annealing facility capable of improving the descaling property of a Si-containing hot-rolled steel sheet without requiring heating of the steel sheet in a mechanical descaling or a pickling step, and to propose a hot-rolled sheet annealing method and a descaling method using the facility.SOLUTION: In a hot-rolled sheet annealing facility having a heating zone, a soaking zone, and a cooling zone for subjecting hot-rolled sheet annealing to a Si-containing hot-rolled steel sheet, when the Si-containing steel sheet is subjected to hot-rolled sheet annealing using the hot-rolled sheet annealing facility provided with a rapid heating device upstream of the heating zone and/or in front of the heating zone, the hot-rolled steel sheet is heated by 50°C or more at a raising rate of temperature of 15°C/s or more in the rapid heating device. A hot-rolled sheet annealing and descaling method capable of descaling with pickling alone is thus provided without applying mechanical descaling prior to pickling.SELECTED DRAWING: Figure 3

Description

本発明は、熱延板焼鈍設備、熱延板焼鈍方法および脱スケール方法に関し、具体的には、方向性電磁鋼板や無方向性電磁鋼板、高強度冷延鋼板等の素材となるＳｉを多量に含有するＳｉ含有熱延鋼板に熱延板焼鈍を施す熱延板焼鈍設備と熱延板焼鈍方法ならびに上記熱延板焼鈍後のＳｉ含有熱延鋼板の脱スケール方法に関するものである。   The present invention relates to a hot-rolled sheet annealing facility, a hot-rolled sheet annealing method, and a descaling method. Specifically, a large amount of Si serving as a material for a directional electromagnetic steel sheet, a non-oriented electromagnetic steel sheet, a high-strength cold-rolled steel sheet, etc. The present invention relates to a hot-rolled sheet annealing facility and a hot-rolled sheet annealing method for performing hot-rolled sheet annealing on the Si-containing hot-rolled steel sheet, and a descaling method of the Si-containing hot-rolled steel sheet after the hot-rolled sheet annealing.

主に電気機器の鉄心材料として用いられる電磁鋼板は、無方向性電磁鋼板と方向性電磁鋼板とに大別されるが、いずれも、鉄損を低減するため、鋼の固有抵抗を高めるＳｉやＡｌを多量に含有しているのが普通である。上記無方向性電磁鋼板は、一般に、所定の成分組成に調整した鋼を溶製し、連続鋳造法等でスラブとした後、熱間圧延し、必要に応じて熱延板焼鈍し、酸洗し、冷間圧延し、一次再結晶させる仕上焼鈍を施すことで、また、方向性電磁鋼板は、一般に、所定の成分組成に調整した鋼を溶製し、連続鋳造法等でスラブとした後、熱間圧延し、必要に応じて熱延板焼鈍し、酸洗し、冷間圧延し、脱炭焼鈍を兼ねた一次再結晶焼鈍し、焼鈍分離剤を塗布した後、二次再結晶させる仕上焼鈍を施すことで製造されている。   Electrical steel sheets that are mainly used as iron core materials for electrical equipment are roughly classified into non-oriented electrical steel sheets and directional electrical steel sheets, all of which can increase the specific resistance of steel in order to reduce iron loss. Usually it contains a large amount of Al. The non-oriented electrical steel sheet is generally prepared by melting steel adjusted to a predetermined component composition, forming a slab by a continuous casting method, etc., hot rolling, hot-rolled sheet annealing as necessary, and pickling. The directionally oriented electrical steel sheet is generally produced by subjecting it to a cold annealing and primary recrystallization. , Hot-rolled, hot-rolled sheet annealed as necessary, pickled, cold-rolled, primary recrystallization annealing also serving as decarburization annealing, and after applying an annealing separator, secondary recrystallization Manufactured by finishing annealing.

ここで、上記熱延板焼鈍は、熱間圧延後の鋼板（熱延板）に焼鈍を施すことによって、熱延板の再結晶不足を解消し、冷間圧延前の結晶粒を粗大化したり整粒化したりすることで、冷間圧延前の鋼板の集合組織を磁気特性に有利なものに改善したり、リジングを防止するために行われる。   Here, the hot-rolled sheet annealing is performed by annealing the steel sheet (hot-rolled sheet) after hot rolling, thereby eliminating the lack of recrystallization of the hot-rolled sheet and coarsening the crystal grains before cold rolling. By adjusting the grain size, the texture of the steel sheet before cold rolling is improved to be advantageous in magnetic properties, and ridging is prevented.

また、酸洗は、熱間圧延や熱延板焼鈍によって鋼板表面に形成された酸化スケールが残存したままの鋼板を冷間圧延すると、圧延ロールによって酸化スケールが鋼板表面に押し込まれて鋼板表面の凹凸が激しくなったり、剥離した酸化スケールが堆積してロール表面に付着し、転写することで表面欠陥を引き起こしたりして、最終製品の表面品質を著しく損なうため、冷間圧延する前に鋼板表面から酸化スケールを除去する（脱スケール）工程であり、電磁鋼板用の熱延鋼板に限らず、冷間圧延する鋼板の製造においては必要不可欠な工程である。なお、上記酸洗液としては、一般に、塩酸や硫酸、弗酸およびそれらの酸を混合した混酸のいずれかの酸が用いられている。   In addition, when pickling is performed by cold rolling a steel sheet in which the oxide scale formed on the steel sheet surface remains by hot rolling or hot-rolled sheet annealing, the oxide scale is pushed into the steel sheet surface by a rolling roll. The surface of the steel plate is cold-rolled before cold rolling because the unevenness becomes violent, the peeled oxide scale accumulates, adheres to the roll surface, and causes surface defects by transferring it to the surface. It is a process that removes oxide scale from (descaling), and is an indispensable process in the production of steel sheets to be cold-rolled as well as hot-rolled steel sheets for electromagnetic steel sheets. As the pickling solution, generally, any one of hydrochloric acid, sulfuric acid, hydrofluoric acid, and a mixed acid obtained by mixing these acids is used.

ＳｉやＡｌを多量に含有する電磁鋼板や高強度冷延鋼板の素材となる熱延鋼板の酸化スケールは、図１に示すように、Ｆｅが鋼板内部から外部へ拡散することによって形成されるＦｅＯやＦｅ３Ｏ４，Ｆｅ２Ｏ３などの外部スケールと、酸素が外部から鋼板内部へ拡散することによって形成されるＳｉＯ２やＦｅ２ＳｉＯ４などのＳｉ酸化物やＡｌ２Ｏ３などからなるサブスケールとで構成されており、脱スケール性が悪いこと、特にＡｌ２Ｏ３を含むサブスケールは、脱スケール性が著しく悪いことが知られている。そのため、Ｓｉ含有熱延鋼板の脱スケールは、図２（ａ）に示したように、酸洗の前に、軽圧下圧延やローラーレベラ、テンションレベラ、ショットブラスト等のメカニカルデスケーリングを組み合わせて行われることが多い。 As shown in FIG. 1, the oxidation scale of a hot rolled steel sheet used as a material for electromagnetic steel sheets and high-strength cold-rolled steel sheets containing a large amount of Si or Al is formed by FeO diffused from the inside of the steel sheet to the outside. And external scales such as Fe 3 O 4 and Fe 2 O 3 , and Si oxides such as SiO 2 and Fe 2 SiO 4 formed by diffusing oxygen from the outside into the steel plate, Al 2 O 3, and the like. It is known that the descaling property is poor, particularly, the subscale containing Al 2 O 3 has a significantly poor descaling property. Therefore, as shown in FIG. 2 (a), descaling of the Si-containing hot-rolled steel sheet is performed by combining mechanical descaling such as light rolling, roller leveler, tension leveler and shot blasting before pickling. Often.

Ｓｉ含有熱延鋼板の脱スケール性を改善する方法としては、酸化スケールの生成自体を抑制する方法と、酸化スケールの剥離を促進する方法の２つがある。
前者の酸化スケールの生成を抑制する方法としては、例えば、特許文献１には、製鋼工程と、熱間圧延工程と、３つ以上の炉域が設けられた無酸化加熱炉部を有する焼ならし炉を用いた焼ならし工程を含む珪素鋼基板の製造方法において、上記無酸化加熱炉部で使用される炉域のエネルギー投入率を１５〜９５％の範囲に調整し、上記無酸化加熱炉部の過剰係数α（実際燃焼空気量の、理論燃焼空気量に対する割合）を０．８≦α＜１．０の範囲内に調節することによって、焼ならし処理プロセスにおける高密度酸化物の形成を抑制する技術が開示されている。しかしこの方法は、実操業においては、エネルギー投入率や過剰係数αの調整によって加熱炉の温度分布が不均一化するため、適切な加熱を施すことが難しいという問題がある。 There are two methods for improving the descalability of the Si-containing hot-rolled steel sheet: a method for suppressing the formation of oxide scale itself and a method for promoting exfoliation of the oxide scale.
As a method for suppressing the former generation of oxide scale, for example, Patent Document 1 discloses a steel making process, a hot rolling process, and a non-oxidizing heating furnace portion provided with three or more furnace zones. In the method for producing a silicon steel substrate including a normalizing step using a furnace, the energy input rate of a furnace region used in the non-oxidation heating furnace is adjusted to a range of 15 to 95%, and the non-oxidation heating By adjusting the excess coefficient α of the furnace section (the ratio of the actual combustion air amount to the theoretical combustion air amount) within the range of 0.8 ≦ α <1.0, the high density oxide in the normalization process A technique for suppressing formation is disclosed. However, this method has a problem that, in actual operation, the temperature distribution of the heating furnace becomes non-uniform by adjusting the energy input rate and the excess coefficient α, so that it is difficult to perform appropriate heating.

また、後者の酸化スケールの剥離を促進する方法としては、前述したショットブラストやテンションレベラ等のメカニカルデシケーリングの採用があるが、Ｓｉ含有量が高い鋼板は、硬質のため破断し易く、重大な操業トラブルを引起こし易いという問題がある。また、酸洗液の濃度や温度を高める方法もあるが、何らかの原因で通板速度が低下した時に過酸洗となり、表面品質に悪影響を及ぼしたり、酸洗時の作業環境を悪化させたりする等の問題がある。   In addition, as a method of promoting the exfoliation of the latter oxide scale, there is the adoption of mechanical desiccation such as the above-mentioned shot blasting or tension leveler, but a steel sheet having a high Si content is hard and easily breaks. There is a problem that it is easy to cause operational troubles. In addition, there is a method to increase the concentration and temperature of the pickling solution, but when the sheeting speed is reduced for some reason, it becomes over pickling, which adversely affects the surface quality and deteriorates the working environment during pickling. There are problems such as.

そこで、特許文献２には、誘導加熱装置で酸洗前の鋼板を加熱し、酸化スケールのクラックを地金表面にまで進行させた後、そのクラック中に酸洗液を吹き込むことで脱スケール性を向上する技術が提案されている。また、特許文献３には、酸洗槽前にスケールブレーカーを設置し、複数個のデフレクターロール、噴射ノズルおよび誘導加熱装置を酸洗槽内に設置して、スケールブレーカーによりスケールにクラックを入れ、その後、デフレクターロールによる曲げによりクラックを開口し、その開口に酸液を噴射し、かつ、化学反応を進行させるために誘導加熱で鋼板温度を上昇させる技術が開示されている。   Therefore, in Patent Document 2, the steel sheet before pickling is heated with an induction heating device, and after the crack of the oxide scale is advanced to the surface of the bare metal, the pickling solution is blown into the crack to remove the scale. A technique for improving the above has been proposed. Further, in Patent Document 3, a scale breaker is installed before the pickling tank, a plurality of deflector rolls, spray nozzles and induction heating devices are installed in the pickling tank, and the scale breaker is cracked by the scale breaker. Thereafter, a technique is disclosed in which a crack is opened by bending with a deflector roll, an acid solution is injected into the opening, and the steel plate temperature is increased by induction heating to advance a chemical reaction.

特表２０１５−５１１９９５号公報Special table 2015-511995 gazette 特開昭６１−０７９７９０号公報JP 61-079790 A 特開平０９−０７８２７３号公報JP 09-078373 A

しかしながら、上記特許文献２に開示の技術は、酸洗前に鋼板が加熱されると、酸洗液が昇温して有害な酸ヒュームが発生したり、鋼板が過酸洗となったり、酸洗槽の耐久性が低下したりする等の問題がある。また、上記特許文献３に開示の技術は、加熱設備等やロール、ノズル等を酸洗槽内に設置する必要があり、機器設備の寿命が短くなったり、メンテナンスが難しくなったりする等の問題がある。   However, in the technique disclosed in Patent Document 2, when the steel sheet is heated before the pickling, the pickling solution is heated to generate harmful acid fume, the steel sheet is over pickled, There is a problem that the durability of the washing tank is lowered. In addition, the technique disclosed in Patent Document 3 requires that heating equipment, rolls, nozzles, and the like be installed in the pickling tank, and that the life of the equipment is shortened and maintenance is difficult. There is.

本発明は、従来技術が抱える上記問題点に鑑みてなされたものであり、その目的は、メカニカルデスケーリングや酸洗工程での鋼板加熱を必要とすることなく、Ｓｉ含有熱延鋼板の脱スケール性を改善することができる熱延板焼鈍設備を提供するとともに、上記設備を用いた熱延板焼鈍方法および脱スケール方法を提案することにある。   The present invention has been made in view of the above-described problems of the prior art, and the object thereof is descaling of a Si-containing hot-rolled steel sheet without requiring steel plate heating in mechanical descaling or pickling processes. The present invention provides a hot-rolled sheet annealing facility capable of improving the performance, and proposes a hot-rolled sheet annealing method and a descaling method using the above-described facility.

発明者らは、上記課題を解決するため、脱スケール性を改善するには酸化スケールの剥離性を高めることが重要であるとの観点から、加熱方法に着目して鋭意検討を重ねた。その結果、鋼板表面の酸化スケール層は、地鉄とは熱膨張係数が異なるため、地鉄と同じ温度に加熱しても酸化スケールと地鉄の間に熱膨張量の違いに起因した熱応力が発生すること、また、鋼板の加熱方法として、鋼板の外部から加熱する輻射加熱ではなく、鋼板自体が発熱する誘導加熱や通電加熱を適用すると、熱伝導性の違いによって地鉄と酸化スケール間に温度差が生じること、さらに、上記誘導加熱や通電加熱を用いて鋼板を急速加熱したときは、地鉄と鋼板間の温度差がより大きくなり、酸化スケールと地鉄の間には著しく大きな熱応力が発生し、その結果、鋼板表面に生成した酸化スケールにクラックが発生し、剥離性が改善されることを知見した。そこで、発明者らは、上記急速加熱を、熱延鋼板に熱延板焼鈍を施す工程において施すことを検討した結果、脱スケール性の改善に著しく効果があることを見出し、本発明を開発するに至った。   In order to solve the above-mentioned problems, the inventors have made extensive studies focusing on the heating method from the viewpoint that it is important to improve the peelability of the oxide scale in order to improve the descalability. As a result, the oxide scale layer on the surface of the steel sheet has a different thermal expansion coefficient from that of the base iron, so even if it is heated to the same temperature as the base iron, the thermal stress due to the difference in thermal expansion between the oxide scale and the base iron In addition, if induction heating or current heating that generates heat from the steel sheet itself is applied as a heating method for the steel sheet, rather than radiant heating that heats from the outside of the steel sheet, there is a difference in thermal conductivity between the steel and the oxide scale. In addition, when the steel plate is rapidly heated using the induction heating or current heating, the temperature difference between the ground iron and the steel plate becomes larger, and the difference between the oxide scale and the steel is extremely large. It has been found that thermal stress is generated, and as a result, cracks are generated in the oxide scale generated on the surface of the steel sheet and the peelability is improved. Therefore, the inventors have found that the rapid heating is performed in the step of subjecting the hot-rolled steel sheet to hot-rolled sheet annealing. As a result, the inventors have found that there is a remarkable effect in improving the descaling property, and develop the present invention. It came to.

すなわち、本発明は、Ｓｉ含有熱延鋼板に熱延板焼鈍を施す、加熱帯、均熱帯および冷却帯を有する熱延板焼鈍設備において、上記加熱帯よりも上流に、および／または、加熱帯内の前段に、急速加熱装置を設けてなることを特徴とする熱延板焼鈍設備である。   That is, the present invention provides a hot-rolled sheet annealing facility having a heating zone, a soaking zone, and a cooling zone for performing hot-rolled sheet annealing on a Si-containing hot-rolled steel plate, upstream of the heating zone and / or the heating zone. It is a hot-rolled sheet annealing facility characterized in that a rapid heating device is provided in the previous stage.

本発明の上記熱延板焼鈍設備における上記急速加熱装置は、誘導加熱装置または通電加熱装置であることを特徴とする。   The rapid heating device in the hot-rolled sheet annealing facility of the present invention is an induction heating device or an electric heating device.

また、本発明は、上記の熱延板焼鈍設備を用いて、Ｓｉ含有熱延鋼板に熱延板焼鈍を施す際、上記急速加熱装置でＳｉ含有熱延鋼板を１５℃／ｓ以上の昇温速度で、５０℃以上加熱することを特徴とする熱延板焼鈍方法である。   In addition, the present invention uses the above-mentioned hot-rolled sheet annealing equipment to heat-treat the Si-containing hot-rolled steel sheet to the Si-containing hot-rolled steel sheet by using the rapid heating device to raise the temperature of the Si-containing hot-rolled steel sheet by 15 ° C./s or more. It is a hot-rolled sheet annealing method characterized by heating at 50 ° C. or higher at a speed.

また、本発明の上記熱延板焼鈍方法は、上記急速加熱装置でＳｉ含有熱延鋼板を加熱するときの加熱開始温度を室温〜６００℃の間とすることを特徴とする。   Moreover, the said hot-rolled sheet annealing method of this invention makes the heating start temperature when heating a Si containing hot-rolled steel plate with the said rapid heating apparatus between room temperature-600 degreeC, It is characterized by the above-mentioned.

また、本発明は、上記の方法で熱延板焼鈍を施したＳｉ含有熱延鋼板に、メカニカルデスケーリングを施すことなく酸洗を施すことを特徴とする脱スケール方法である。   Moreover, this invention is a descaling method characterized by performing pickling without performing mechanical descaling to Si containing hot-rolled steel plate which performed hot-rolled sheet annealing by said method.

また、本発明は、上記の方法で熱延板焼鈍を施したＳｉ含有熱延鋼板に、メカニカルデスケーリングを施した後、酸洗を施すことを特徴とする脱スケール方法である。   Moreover, this invention is a descaling method characterized by performing pickling after performing mechanical descaling to the Si containing hot-rolled steel plate which performed the hot-rolled sheet annealing by said method.

また、本発明の上記脱スケール方法が対象とする上記Ｓｉ含有熱延鋼板は、Ｓｉを１．０ｍａｓｓ％以上含有するものであることを特徴とする   In addition, the Si-containing hot-rolled steel sheet targeted by the descaling method of the present invention is characterized by containing Si by 1.0 mass% or more.

また、本発明の上記脱スケール方法が対象とする上記Ｓｉ含有熱延鋼板は、電磁鋼板用の素材であることを特徴とする。   The Si-containing hot-rolled steel sheet targeted by the descaling method of the present invention is a material for an electromagnetic steel sheet.

本発明によれば、Ｓｉ含有熱延鋼板に熱延板焼鈍を施す焼鈍設備に急速加熱装置を設置し、所定の昇温速度以上かつ所定の温度量以上の急速加熱を施すことで、酸化スケールにクラックを導入し、剥離性を改善するので、メカニカルデスケーリングを施すことなく、酸洗のみで鋼板表面の酸化スケールを除去することが可能となる。
その結果、本発明によれば、Ｓｉ含有熱延鋼板の酸洗能率を高めたり、酸洗工程を大幅に簡素化したりすることが可能となるだけでなく、表面品質に優れた製品を安定して製造することが可能となる。
さらに、本発明によれば、鋼板を急速加熱するのに用いる加熱装置が、熱延板焼鈍設備の加熱帯の一部として機能するため、熱エネルギー効率の向上にも寄与する。 According to the present invention, an oxide scale is obtained by installing a rapid heating apparatus in an annealing facility for performing hot-rolled sheet annealing on a Si-containing hot-rolled steel sheet, and performing rapid heating at a predetermined temperature increase rate or more and a predetermined temperature amount or more. Since cracks are introduced to improve the peelability, it is possible to remove the oxidized scale on the surface of the steel sheet only by pickling without performing mechanical descaling.
As a result, according to the present invention, not only can the pickling efficiency of the Si-containing hot-rolled steel sheet be increased or the pickling process can be greatly simplified, but also a product with excellent surface quality can be stabilized. Can be manufactured.
Furthermore, according to this invention, since the heating apparatus used for rapidly heating a steel plate functions as a part of the heating zone of a hot-rolled sheet annealing facility, it contributes also to the improvement of thermal energy efficiency.

Ｓｉ含有熱延鋼板の表面に形成された酸化スケールの断面構造を説明する図である。It is a figure explaining the cross-sectional structure of the oxide scale formed in the surface of Si containing hot-rolled steel plate. 本発明と従来技術の脱スケール工程の設備列を比較して示した図である。It is the figure which compared and showed the equipment row | line | column of the descaling process of this invention and a prior art. 本発明と従来技術の熱延板焼鈍後、メカニカルデスケーリング後および酸洗後のＳｉ含有熱延鋼板の減量を比較して示した図である。It is the figure which compared and showed the weight loss of the Si-containing hot-rolled steel sheet after mechanical descaling and after pickling after the hot-rolled sheet annealing of the present invention and the prior art.

発明者らは、先述したように、Ｓｉ含有熱延鋼板の脱スケール性を改善するためには、酸化スケールの剥離性を高めることが重要であるとの観点から、鋼板の加熱方法の違い、すなわち、鋼板を外部から緩速加熱する輻射加熱と、鋼板の内部から急速加熱する誘導加熱や直接通電加熱との違いが、脱スケール性に及ぼす影響に着目した。
というのは、熱延鋼板の表面に形成された酸化スケールは、前述した図１に示したように成分組成が異なる複数の層から構成されているが、いずれの層も地鉄と熱膨張係数が大きく異なるため、地鉄と同じ温度に加熱しても、スケールと地鉄の間に熱膨張量差に起因した熱応力が発生する。 As described above, in order to improve the descalability of the Si-containing hot-rolled steel sheet, the inventors considered that it is important to increase the peelability of the oxide scale, and the difference in the heating method of the steel sheet, That is, we focused on the influence of the difference between radiation heating, which heats a steel sheet from the outside, and induction heating, which directly heats the steel sheet from the inside, or direct current heating, on the descaling property.
This is because the oxide scale formed on the surface of the hot-rolled steel sheet is composed of a plurality of layers having different component compositions as shown in FIG. 1 described above. Therefore, even when heated to the same temperature as the base iron, thermal stress is generated between the scale and the base iron due to the difference in thermal expansion.

さらに、鋼板を外部から加熱する輻射加熱の場合には、酸化スケールが加熱されてから鋼板が加熱されるため、両者間で大きな温度差は生じないが、誘導加熱等で加熱した場合には、鋼板自体が発熱するため、酸化スケールと地鉄間に温度差が生じる。さらに、誘導加熱等の場合には、急速加熱が可能であるため、輻射加熱のような熱伝導による緩速加熱と比較し、酸化スケールと地鉄間との温度差はより拡大される。その結果、酸化スケールと地鉄間との間には熱膨張差に起因して大きな熱応力が発生し、酸化スケールに微小なき裂（クラック）が多数発生し、酸化スケールの剥離が促進され、脱スケール性が改善されることが期待されるからである。   Furthermore, in the case of radiant heating that heats the steel sheet from the outside, since the steel sheet is heated after the oxide scale is heated, a large temperature difference does not occur between the two, but when heated by induction heating or the like, Since the steel plate itself generates heat, a temperature difference is generated between the oxide scale and the ground iron. Furthermore, in the case of induction heating or the like, rapid heating is possible, and therefore, the temperature difference between the oxide scale and the ground iron is further expanded as compared with slow heating by heat conduction such as radiation heating. As a result, a large thermal stress is generated between the oxide scale and the base metal due to the difference in thermal expansion, a large number of small cracks are generated in the oxide scale, and the exfoliation of the oxide scale is promoted. This is because descalability is expected to be improved.

そこで、発明者らは、上記考えの妥当性を確認するため、以下の実験を行った。
＜実験１＞
Ｓｉを３．０ｍａｓｓ％含有する（無）方向性電磁鋼板用の熱延鋼板（熱延板）から、試験片を採取し、この熱延板に対して１０５０℃×６０ｓの熱延板焼鈍を模擬した熱処理を施した。この際、上記熱処理における加熱は、室温（２０℃）から３０℃、５０℃、７０℃、１００℃、４００℃および７００℃までを、ソレノイド式誘導加熱装置を用いて、昇温速度５０℃／ｓで急速加熱し、その後、上記急速加熱後のそれぞれの温度から１０５０℃までを、直火式加熱炉（輻射式加熱炉）を用いて加熱し、６０ｓ間保持した後、２５℃／ｓで冷却した。なお、上記熱処理時の雰囲気は窒素雰囲気とした。 Therefore, the inventors conducted the following experiment in order to confirm the validity of the above idea.
<Experiment 1>
A test piece was taken from a hot rolled steel sheet (hot rolled sheet) for a (non) grain-oriented electrical steel sheet containing 3.0 mass% of Si, and subjected to hot rolled sheet annealing at 1050 ° C. × 60 s with respect to the hot rolled sheet. Simulated heat treatment was applied. At this time, the heating in the heat treatment is performed at room temperature (20 ° C.) to 30 ° C., 50 ° C., 70 ° C., 100 ° C., 400 ° C. and 700 ° C. using a solenoid induction heating device at a temperature rising rate of 50 ° C. / After heating rapidly with s, each temperature after the rapid heating up to 1050 ° C. is heated using a direct heating furnace (radiant heating furnace), held for 60 s, and then at 25 ° C./s Cooled down. Note that the atmosphere during the heat treatment was a nitrogen atmosphere.

次いで、上記熱処理後の試験片を、８０℃の温度に保持した８ｍａｓｓ％ＨＣｌ水溶液中に６０ｓ間浸漬する酸洗を行い、酸洗後鋼板表面の酸化スケールの剥離状況を目視観察し、脱スケール性を評価した。
なお、上記脱スケール性の評価基準は、脱スケール後の表面外観が、従来のＳｉ含有熱延鋼板の脱スケール法（メカニカルデスケーリング＋酸洗）と同等以上のものを脱スケール性が優（〇）、従来の脱スケール法（メカニカルデスケーリング＋酸洗）より劣るが、従来の酸洗のみの場合よりも良好なものを脱スケール性が劣（△）、従来の酸洗のみの場合と同等のものを脱スケール性が悪（×）とした。 Next, the heat-treated test piece is pickled by immersing it in an 8 mass% HCl aqueous solution maintained at a temperature of 80 ° C. for 60 s. After pickling, the state of peeling of the oxide scale on the steel sheet surface is visually observed, and descaling is performed. Sex was evaluated.
In addition, the above-mentioned evaluation criteria for descalability are excellent in descalability when the surface appearance after descaling is equal to or greater than the conventional descaling method (mechanical descaling + pickling) of Si-containing hot-rolled steel sheets ( ◯) Inferior to conventional descaling method (mechanical descaling + pickling), but better than conventional pickling alone (△) An equivalent one was considered to have a bad descalability (×).

上記評価の結果を表１に示した。この結果から、誘導加熱で昇温速度５０℃／ｓで急速加熱する場合には、昇温量を５０℃以上とすることによって、脱スケール性が、酸洗のみでも、メカニカルデスケーリングと酸洗を組み合わせた従来条件よりも改善されることがわかった。   The results of the evaluation are shown in Table 1. From this result, in the case of rapid heating at a heating rate of 50 ° C./s by induction heating, the descaling property can be reduced by mechanical descaling and pickling only by pickling by setting the heating rate to 50 ° C. or higher. It was found that the condition was improved over the conventional conditions.

＜実験２＞
次に、上記＜実験１＞の結果に基き、室温（２０℃）からの昇温量を５０℃、すなわち、加熱温度を７０℃（一定）とし、昇温速度を５℃／ｓ、１０℃／ｓ、１５℃／ｓ、２０℃／ｓおよび５０℃／ｓの４水準に変化させ、その他の条件、および脱スケール性の評価基準は上記＜実験１＞と同様とすることによって、鋼板の昇温速度が脱スケール性に及ぼす影響を調査した。 <Experiment 2>
Next, based on the result of <Experiment 1>, the temperature rise from room temperature (20 ° C.) is 50 ° C., that is, the heating temperature is 70 ° C. (constant), and the temperature rise rate is 5 ° C./s, 10 ° C. / S, 15 ° C./s, 20 ° C./s, and 50 ° C./s, and other conditions and evaluation criteria for descalability are the same as in the above <Experiment 1>. The effect of heating rate on descalability was investigated.

その結果を、表２に示した。この結果から、誘導加熱にいる昇温量を５０℃（一定）とした場合、１５℃／ｓ以上で急速加熱することで、酸洗のみにおける脱スケール性が、メカニカルデスケーリングと酸洗とを組み合わせた従来条件と同等以上に改善されることがわかった。   The results are shown in Table 2. From this result, when the amount of temperature rise in induction heating is 50 ° C. (constant), the descalability only in pickling can be achieved by mechanical descaling and pickling by rapid heating at 15 ° C./s or more. It was found that the improvement was equivalent to or better than the combined conventional conditions.

上記＜実験１＞および＜実験２＞の結果から、熱延板焼鈍の加熱過程で、誘導加熱を用いて急速加熱を行う場合には、昇温速度を１５℃／ｓ以上、かつ、昇温量を５０℃以上とすることによって、酸洗前にメカニカルデスケーリングを施したときと同等以上の脱スケール性改善効果が得られること、したがって、熱延板焼鈍の加熱過程において熱延板を上記条件を満たして加熱した場合には、酸洗前に行っていたメカニカルデスケーリングを省略しても、従来技術と同等以上の脱スケール性を達成できることが明らかとなった。
本発明は、上記の新規な知見に基くものである。 From the results of <Experiment 1> and <Experiment 2>, when performing rapid heating using induction heating in the heating process of hot-rolled sheet annealing, the rate of temperature increase is 15 ° C./s or more and the temperature is increased. By setting the amount to 50 ° C. or higher, the descalability improvement effect equivalent to or higher than that obtained when mechanical descaling is performed before pickling can be obtained. Therefore, in the heating process of hot rolled sheet annealing, When heating was performed while satisfying the conditions, it became clear that even when mechanical descaling that was performed before pickling was omitted, descalability equal to or higher than that of the prior art could be achieved.
The present invention is based on the above novel findings.

次に、本発明について具体的に説明する。
まず、本発明が対象とする熱延鋼板は、Ｓｉを１．０ｍａｓｓ％以上含有するものであることが好ましい。１．０ｍａｓｓ％未満では、酸洗における脱スケール性の低下が顕著でないため、酸洗前のメカニカルデスケーリングを必須としないためである。ただし、本発明をＳｉ：１．０ｍａｓｓ％未満の熱延鋼板に適用してもよいことは勿論である。なお、Ｓｉの上限は特に制限しないが、製造ラインへの通板性確保の観点から、上限は５．０ｍａｓｓ％程度である。好ましくは１．８〜４．０ｍａｓｓ％の範囲である。 Next, the present invention will be specifically described.
First, the hot-rolled steel sheet targeted by the present invention preferably contains 1.0% by mass or more of Si. If it is less than 1.0 mass%, the decrease in descalability in pickling is not significant, and mechanical descaling before pickling is not essential. However, it is needless to say that the present invention may be applied to a hot-rolled steel sheet having a Si content of less than 1.0 mass%. In addition, although the upper limit of Si is not particularly limited, the upper limit is about 5.0 mass% from the viewpoint of ensuring the plateability to the production line. Preferably it is the range of 1.8-4.0 mass%.

なお、上記の範囲でＳｉを含有する熱延鋼板としては、具体的には、方向性電磁鋼板や無方向性電磁鋼板の素材と熱延鋼板や、高強度冷延鋼板や高強度表面処理鋼板の素材となる熱延鋼板などがあり、いずれも表面性状が優れることが求められるものである。   In addition, as a hot-rolled steel sheet containing Si in the above range, specifically, a directional electromagnetic steel sheet or a non-oriented electromagnetic steel sheet and a hot-rolled steel sheet, a high-strength cold-rolled steel sheet, or a high-strength surface-treated steel sheet There are hot-rolled steel sheets and the like that are used as the raw materials, and all are required to have excellent surface properties.

また、本発明を適用する熱延板焼鈍設備は、連続焼鈍炉であることが好ましい。バッチ式（箱型）の焼鈍炉では、急速加熱が不可能であるからである。   Moreover, it is preferable that the hot-rolled sheet annealing equipment to which this invention is applied is a continuous annealing furnace. This is because rapid heating is impossible in a batch-type (box-type) annealing furnace.

また、上記急速加熱に用いる加熱装置は、鋼板自体から発熱し、かつ、急速加熱することができる誘導加熱装置か通電加熱装置であることが好ましい。なお、誘導加熱装置の場合には、トランスバース式よりも、鋼板を幅方向で均一に加熱するのに適したソレノイド式の方が好ましい。   Moreover, it is preferable that the heating apparatus used for the rapid heating is an induction heating apparatus or an electric heating apparatus that generates heat from the steel plate itself and can be rapidly heated. In the case of an induction heating device, a solenoid type suitable for heating a steel plate uniformly in the width direction is preferable to a transverse type.

また、前述した＜実験１＞および＜実験２＞からわかるように、熱延板焼鈍においてＳｉ含有熱延鋼板の脱スケール性の改善するためには、鋼板の昇温速度を１５℃／ｓ以上として、５０℃以上の昇温量の急速加熱を行うことが必要である。ここで、上記昇温速度は、地鉄と酸化スケールとの間の温度差を大きくする観点から、３０℃／ｓ以上とするのが好ましく、５０℃／ｓ以上とするのがより好ましい。また、上記急速加熱の昇温量は、同じ観点から、５０℃以上とするのが好ましく、８０℃以上とするのがより好ましい。ただし、急速加熱する終点温度が７００℃を超えると、加熱に大電流が必要となったり、加熱装置も大掛かりなものとなったりする。さらに、ソレノイド式誘導加熱の場合、鋼板温度がキュリー点を超えると、加熱効率が急激に低下するので、急速加熱の上限は７００℃程度とするのが好ましい。   Further, as can be seen from <Experiment 1> and <Experiment 2> described above, in order to improve the descalability of the Si-containing hot-rolled steel sheet in hot-rolled sheet annealing, the heating rate of the steel sheet is set to 15 ° C./s or more. As described above, it is necessary to perform rapid heating with a temperature rise of 50 ° C. or higher. Here, the temperature increase rate is preferably 30 ° C./s or more, and more preferably 50 ° C./s or more, from the viewpoint of increasing the temperature difference between the base iron and the oxide scale. Further, from the same viewpoint, the temperature increase amount of the rapid heating is preferably 50 ° C. or higher, and more preferably 80 ° C. or higher. However, if the end point temperature for rapid heating exceeds 700 ° C., a large current is required for heating, and the heating apparatus becomes large. Furthermore, in the case of solenoid induction heating, when the steel plate temperature exceeds the Curie point, the heating efficiency is drastically lowered, so the upper limit of rapid heating is preferably about 700 ° C.

また、上記熱延板焼鈍設備に急速加熱装置を設置する位置は、加熱帯よりも上流（加熱帯の直前）、および／または、加熱帯内とすることが好ましい。なお、急速加熱装置を加熱帯の直前に設置する場合には問題とならないが、加熱帯内に設置する場合には、誘導加熱コイルや通電ロールの熱損傷を防止する観点から、加熱帯内の前段（最上流側）、より好ましくは炉内温度が６００℃以下の領域とするのが好ましい。したがって、鋼板を急速加熱する開始温度は、室温〜１００℃の範囲とするのが好ましい。   Moreover, it is preferable that the position where the rapid heating apparatus is installed in the hot-rolled sheet annealing facility is upstream of the heating zone (immediately before the heating zone) and / or within the heating zone. It should be noted that there is no problem when the rapid heating device is installed immediately before the heating zone. However, when it is installed within the heating zone, the heating zone can be installed in the heating zone from the viewpoint of preventing thermal damage to the induction heating coil and the energizing roll. It is preferable to set the temperature in the previous stage (uppermost stream side), more preferably in the region where the furnace temperature is 600 ° C. or lower. Therefore, it is preferable that the starting temperature for rapidly heating the steel sheet is in the range of room temperature to 100 ° C.

上記条件で急速加熱を施した熱延板焼鈍後のＳｉ含有熱延鋼板は、鋼板表面に形成された酸化スケールに微細なクラックが多数導入され、酸化スケールの剥離性が向上しているので、酸洗前にメカニカルデスケーリングなしでも、メカニカルデスケーリングを施したときと同等以上の脱スケール性を得ることができる。したがって、Ｓｉ含有熱延鋼板の酸洗工程では、従来、図２（ａ）に示したように、酸洗前のメカニカルデスケーリング工程は必須の工程であったが、例えば、図２（ｂ）に示したように、熱延板焼鈍設備の加熱帯の直前に急速加熱装置を設置することで、該メカニカルデスケーリング工程を省略することが可能となる。また、上記図２（ｂ）では、加熱帯の直前に設置した例を示したが、加熱帯内上流側の低温度域に設けてもよい。ただし、酸洗性をより改善するために、メカニカルデスケーリングを施してもよいことは勿論である。   Since the Si-containing hot-rolled steel sheet after hot-rolled sheet annealing that has been subjected to rapid heating under the above conditions has many fine cracks introduced into the oxide scale formed on the surface of the steel sheet, the peelability of the oxide scale is improved. Even without mechanical descaling before pickling, a descaling property equal to or better than that obtained when mechanical descaling is performed can be obtained. Therefore, in the pickling process of the Si-containing hot-rolled steel sheet, as shown in FIG. 2 (a), the mechanical descaling process before pickling has been an indispensable process. For example, FIG. 2 (b) As shown in the above, the mechanical descaling step can be omitted by installing a rapid heating device immediately before the heating zone of the hot-rolled sheet annealing equipment. Moreover, although the example installed in front of the heating zone is shown in FIG. 2B, it may be provided in a low temperature region on the upstream side in the heating zone. However, it goes without saying that mechanical descaling may be applied in order to further improve the pickling performance.

Ｓｉを３．５ｍａｓｓ％含有する板厚が２．５ｍｍの電磁鋼板用の熱延鋼板から幅：１００ｍｍ×長さ：３００ｍｍの試験片を採取し、以下に示した熱延板焼鈍を模擬した条件ＡおよびＢの熱処理を施した。なお、条件ＡおよびＢとも焼鈍時の雰囲気はＮ２雰囲気とした。
＜熱延板焼鈍条件＞
・条件Ａ：直火式サイドバーナ加熱炉を模擬した実験炉（輻射式加熱炉）で、室温（２０℃）から１０５０℃までを１０℃／ｓで加熱し、１０５０℃で４０秒間保持した後、２５℃／ｓで冷却する。
・条件Ｂ：誘導加熱装置を用いて室温（２０℃）から７００℃まで６０℃／ｓで急速加熱した後、上記条件Ａで用いた輻射式加熱炉で７００℃から１０５０℃まで２０℃／ｓで加熱し、１０５０℃で４０秒間保持した後、２５℃／ｓで冷却する。 A test piece of width: 100 mm × length: 300 mm was sampled from a hot rolled steel sheet for an electromagnetic steel sheet containing 2.5 mass% of Si and having a thickness of 2.5 mm, and simulated conditions of hot rolled sheet annealing shown below. A and B were heat-treated. In both conditions A and B, the atmosphere during annealing was an N 2 atmosphere.
<Hot rolled sheet annealing conditions>
-Condition A: After heating at 10 ° C / s from room temperature (20 ° C) to 1050 ° C in an experimental furnace (radiation-type heating furnace) simulating a direct-fired side burner heating furnace, held at 1050 ° C for 40 seconds Cool at 25 ° C./s.
Condition B: After rapid heating at 60 ° C./s from room temperature (20 ° C.) to 700 ° C. using an induction heating device, 20 ° C./s from 700 ° C. to 1050 ° C. in the radiant heating furnace used in the above condition A After heating at 1050 ° C. for 40 seconds, it is cooled at 25 ° C./s.

次いで、上記熱延板焼鈍後の試験片を長さ方向で２等分し、一方には、下記の条件でメカニカルデスケーリング（ショットブラスト）を施し、もう一方には、メカニカルデスケーリングを施さなかった。
＜ショットブラスト条件＞
・投射材の種類：粒径０．３５±０．１５ｍｍ、スチールショット粒、密度７．５ｇ／ｃｍ３、硬度４０〜５０Ｒｃ
・投射圧力（速度）：１２．５ｋｇ／ｍ２
・投射角度：９０°
・投射量×時間：１０００（ｇ／ｓ）×１５（ｓ） Next, the test piece after the hot-rolled sheet annealing is divided into two equal parts in the length direction, one side is subjected to mechanical descaling (shot blasting) under the following conditions, and the other is not subjected to mechanical descaling. It was.
<Shot blasting conditions>
・ Type of projection material: particle size 0.35 ± 0.15 mm, steel shot particle, density 7.5 g / cm 3 , hardness 40-50Rc
Projection pressure (speed): 12.5 kg / m 2
・ Projection angle: 90 °
Projection amount x time: 1000 (g / s) x 15 (s)

その後、上記長さ方向に２等分した試験片を、さらに幅方向に２等分して、一方の試験片には下記条件ａで、もう一方の試験片には下記条件ｂで酸洗し、脱スケールした。
＜酸洗条件＞
・条件ａ：８０℃の８ｍａｓｓ％のＨＣｌ水溶液中に２０ｓ間浸漬
・条件ｂ：８０℃の８ｍａｓｓ％のＨＣｌ水溶液中に４０ｓ間浸漬
因みに、従来の酸洗前にメカニカルデスケーリングを施した後、上記酸洗条件で酸洗するときの脱スケール所要時間（酸洗時間）は約６０秒である。 Thereafter, the test piece divided in half in the length direction is further divided in half in the width direction, and one test piece is pickled under the following condition a, and the other test piece is pickled under the following condition b. , Descaling.
<Pickling conditions>
・ Condition a: Soaked in 8 mass% HCl aqueous solution at 80 ° C. for 20 s ・ Condition b: Soaked in 8 mass% HCl aqueous solution at 80 ° C. for 40 s After performing mechanical descaling before pickling, The time required for descaling (pickling time) when pickling under the above pickling conditions is about 60 seconds.

上記熱延板焼鈍後、メカニカルデスケーリング後および酸洗後の各段階における試験片の減量（ｇ／ｍ２）を図３に示した。
この結果から、熱延板焼鈍の加熱過程を誘導加熱で７００℃まで急速加熱した試験片は、メカニカルデスケーリングを施さなくとも、すなわち、酸洗のみでも、メカニカルデスケーリングを施したときと同等の脱スケール性を有していることがわかる。また、誘導加熱で７００℃まで急速加熱した試験片は、通常の酸洗時間６０秒から、４０秒や２０秒に短縮しても、表面の酸化スケールが十分に除去されていることがわかる。したがって、本願発明によれば、脱スケール工程から、メカニカルデスケーリング工程を省略できるだけでなく、酸洗時間も短縮できることがわかる。 The weight loss (g / m 2 ) of the test piece at each stage after the hot-rolled sheet annealing, after mechanical descaling and after pickling is shown in FIG.
From this result, the test piece rapidly heated to 700 ° C. by induction heating in the heating process of hot-rolled sheet annealing is equivalent to the case where mechanical descaling is performed without mechanical descaling, that is, pickling alone. It can be seen that it has descalability. Further, it can be seen that the test piece rapidly heated to 700 ° C. by induction heating has the surface oxidized scale sufficiently removed even when the normal pickling time is shortened from 60 seconds to 40 seconds or 20 seconds. Therefore, according to the present invention, it can be seen from the descaling step that not only the mechanical descaling step can be omitted, but also the pickling time can be shortened.

本発明の技術は、Ｓｉ含有の有無に拘わらず脱スケール性の改善効果が得られるので、電磁鋼板や高強度鋼板用のＳｉ含有熱延鋼板のみならず、Ｓｉを含有しない一般熱延鋼板にも適用することができる。

Since the technology of the present invention can improve the descalability regardless of the presence or absence of Si, it can be applied not only to Si-containing hot-rolled steel sheets for electromagnetic steel sheets and high-strength steel sheets, but also to general hot-rolled steel sheets not containing Si. Can also be applied.

Claims (8)

Ｓｉ含有熱延鋼板に熱延板焼鈍を施す、加熱帯、均熱帯および冷却帯を有する熱延板焼鈍設備において、
上記加熱帯よりも上流におよび／または加熱帯内の前段に、急速加熱装置を設けてなることを特徴とする熱延板焼鈍設備。 In the hot-rolled sheet annealing equipment having a heating zone, a soaking zone and a cooling zone, subjecting the Si-containing hot-rolled steel plate to hot-rolled plate annealing,
A hot-rolled sheet annealing facility comprising a rapid heating device upstream of the heating zone and / or upstream of the heating zone. 上記急速加熱装置は、誘導加熱装置または通電加熱装置であることを特徴とする請求項１に記載の熱延板焼鈍設備。 The hot-rolled sheet annealing equipment according to claim 1, wherein the rapid heating apparatus is an induction heating apparatus or an energization heating apparatus. 請求項１または２に記載の熱延板焼鈍設備を用いて、Ｓｉ含有熱延鋼板に熱延板焼鈍を施す際、上記急速加熱装置でＳｉ含有熱延鋼板を１５℃／ｓ以上の昇温速度で、５０℃以上加熱することを特徴とする熱延板焼鈍方法。 When performing hot-rolled sheet annealing on a Si-containing hot-rolled steel sheet using the hot-rolled sheet annealing facility according to claim 1, the temperature of the Si-containing hot-rolled steel sheet is increased by 15 ° C./s or more with the rapid heating device. A hot-rolled sheet annealing method characterized by heating at 50 ° C. or higher at a speed. 上記急速加熱装置でＳｉ含有熱延鋼板を加熱するときの加熱開始温度を室温〜６００℃の間とすることを特徴とする請求項３に記載の熱延板焼鈍方法。 The hot-rolled sheet annealing method according to claim 3, wherein a heating start temperature when heating the Si-containing hot-rolled steel sheet with the rapid heating apparatus is between room temperature and 600 ° C. 請求項３または４に記載の方法で熱延板焼鈍を施したＳｉ含有熱延鋼板に、メカニカルデスケーリングを施すことなく酸洗を施すことを特徴とする脱スケール方法。 A descaling method characterized by subjecting the Si-containing hot-rolled steel sheet subjected to hot-rolled sheet annealing by the method according to claim 3 or 4 to pickling without performing mechanical descaling. 請求項３または４に記載の方法で熱延板焼鈍を施したＳｉ含有熱延鋼板に、メカニカルデスケーリングを施した後、酸洗を施すことを特徴とする脱スケール方法。 A descaling method, comprising subjecting a Si-containing hot-rolled steel sheet subjected to hot-rolled sheet annealing by the method according to claim 3 or 4 to mechanical descaling and then pickling. 上記Ｓｉ含有熱延鋼板は、Ｓｉを１．０ｍａｓｓ％以上含有するものであることを特徴とする請求項５または６に記載の脱スケール方法。 The descaling method according to claim 5 or 6, wherein the Si-containing hot-rolled steel sheet contains 1.0 mass% or more of Si. 上記Ｓｉ含有熱延鋼板は、電磁鋼板用の素材であることを特徴とする請求項５〜７のいずれか１項に記載の脱スケール方法。
The descaling method according to any one of claims 5 to 7, wherein the Si-containing hot-rolled steel sheet is a material for an electromagnetic steel sheet.
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